...and toxic chemicals from the blood.

...and toxic chemicals from the blood

Biochemical engineers at the Massachusetts Institute of Technology is Cambridge have covalently bonded microscopic plastic beads to enzymes derived from microbes. In animal tests, blood filters containing the bead-bound enzymes efficiently and selectively broke down the chemicals against which they were targeted, reports Robert Langer, leader of the filtering systems' design team.

In tests with about 50 sheep, external blood filters containing the bacterial enzyme heparinase removed 99 percent of the anticoagulant drug heparin within about 15 minutes. In similar experiments using 20 rats with jaundice -- caused by a toxic buildup of bilirubin (a brain-damaging, yellow degradation product of hemoglobin) -- a bead-bound fungal enzyme harmlessly broke down all of the bilirubin in filtered blood.

Blood sampled from treated animals showed that 50 percent of the toxic compound -- heparin or bilirubin -- still circulated in the body, perhaps the result of a replenishing from stored residues in tissues. The enzyme filtering was sufficient, however, to reduce body concentrations to nontoxic levels, Langer notes. He anticipates that heparinase treatment, now under consideration for commercial development, may eventually be used in patients undergoing open-heart surgery. He adds that a similar, quick external filtering of blood from severely jaundiced newborns -- perhaps through the umbilicus -- may one day eliminate their need for potentially dangerous blood transfusions.